Cassin's kingbird (Tyrannus vociferans) is a large tyrant flycatcher native to western North America. The name of this bird commemorates the American ornithologist John Cassin.

Adults have a gray head with slightly darker cheeks; a dark unforked tail with a buffy fringe and gray-olive underparts. They have a pale throat and deep yellow lower breast.

Juveniles are duller and have pale edges on their wings.

Measurements:

Length: 8.3–9.1 in (21–23 cm)

Weight: 1.6 oz (45 g)

Wingspan: 41 cm

Cassin's kingbird and the western kingbird are similar in appearance. Cassin's is a little larger than the western and the upper parts are a darker gray than the western. The most distinctive difference between these birds is that the Cassin's has a thin white edge along the distal end of the tail feathers, while the western kingbird has a thin white edge that runs along the side of the tail feathers. This difference can be seen in the adjacent image.